Jorge, can you do a bit of testing to try to narrow down the problem.
Please test if its happening consistantly or just from one page. Trying to access acs-admin while not logged in is how I usually test this.
If the problem is not consistant take a look at the code that is initicating the redirect.
If its consistant everywhere in your site take a look at your kernal parameters, sanity check them all. Try it with and without force_host_p.
